Studies of scotopic retinal function of normal human infants, ages 4 and 10 weeks, and adult control subjects are to be continued. The purpose is to further delineate the determinants of scotopic sensitivity and to consider mechanisms governing scotopic performance in normally developing human infants. Psychophysical, electroretinographic (ERG), pupillographic and optokinetic nystagmus (OKN) responses, each drawing from different levels of visual system activity, will, in and of themselves, give some information about the flow of scotopic signals along the visual pathways. Spectral sensitivity is to be studied in the detail necessary to make valid comparisons to extracted rhodopsin spectra. Also, the development of (1) ERG oscillatory potentials, (2) scotopic spatial vision (including "Westheimer functions"), and (30 dark adapted OKN thresholds are to be investigated. In the future the techniques and concepts evolving from these studies may be applied to the evaluation of human diseases.